ABSTRACT
An analysis of regeneration in annelids has brought to light a whole range of new findings. In them, regeneration is a fairly complex but an orderly process, and proceeds from wound-healing to blastema formation and differentiation, subsequently from segmental reorganization to growth and elongation. It ranges from some hirudineans that cannot even heal the wound to regeneration of an entire worm out of a single segment. The number of species with regenerative potency for anterior, posterior and anterior cum posterior body is 149, 206 and 143, respectively. When the respective numbers are related to 13,012 polychaetes and 3,175 oligochaetes species, the percentage values indicate that the potency is 1.5-2.0 times more prevalent in oligochaetes. In errant polychaetes, the posterior regeneration is induced by neurosecretion from the ‘brain’ but from the ventral ganglia in sedentary worms. In oligochaetes, inadequate reserves in chloragogue temporarily separate the incidences of regeneration and reproduction. However, sedentary polychaetes undertake them together but at reduced reproductive output.
